Hypergraph-Based Interconnection Networks for Large Multicomputers

This thesis deals with issues pertaining to multicomputer interconnection networks namely topology, technology, switching method, and routing algorithm. It argues that a new class of regular low-dimensional hypergraph networks, the distributed crossbar switch hypermesh (DCSH), represents a promising alternative high-performance interconnection network for future large multicomputers to graph networks such as meshes, tori, and binary n-cubes, which have been widely used in current multicomputers. Channels in existing hypergraph and graph structures suffer from bandwidth limitations imposed by implementation technology. The first part of the thesis shows how the low-dimensional DCSH can use an innovative implementation scheme to alleviate this problem. It relies on the separation of processing and communication functions by physical layering in order to accommodate high wiring density and necessary message buffering, improving performance considerably. Various mathematical models of the DCSH, validated through discrete-event simulation, are then introduced. Effects of different switching methods (e.g., wormhole routing, virtual cut-through, and message switching), routing algorithms (e.g., restricted and random), and different switching element designs are investigated. Further, the impact on performance of different communication patterns, such as those including locality and hot-spots, are assessed. The remainder of the thesis compares the DCSH to other common hypergraph and graph networks assuming different implementation technologies, such as VLSI, multiple-chip technology, and the new layered implementation scheme. More realistic assumptions are introduced such as pipeline-bit transmission and non-zero delays through switching elements. The results show that the proposed structure has superior characteristics assuming equal implementation cost in both VLSI and multiple-chip technology. Furthermore, optimal performance is offered by the new layered implementation

Performance Evaluation of SDN-WISE in Mobile Wireless Sensors Networks

Wireless Sensors Networks (WSNs) are the backbone of numerous IoT applications such as smart homes, smart cities, smart farming, smart health, and weather monitoring. Software-Defined Networking (SDN) is an emerging communication paradigm that aims to facilitate the management of WSNs and extend their lifetime by shifting the heavy and energy consuming task of routing from sensors to a powerful and unlimited energy server, named the controller. SDN-WISE is a popular SDN implementation for WSNs. This framework has been evaluated and tested in static WSNs where the sensors have fixed positions. However, most IoT applications incorporate mobile nodes such as robots, self-driving cars, and unmanned aerial vehicles, hence the need of evaluating this framework in mobile WSNs. In this paper, we implement mobility scenarios in SDN-WISE. We then conduct an analysis of the performance of SDN-WISE in both static and mobile scenarios. Our simulation results reveal that SDN-WISE achieves a poor performance in mobile WSNs compared to the static counterparts. This stresses the urgent need to develop efficient routing protocols to handle mobility in SDN-WISE

Optimization of the Deployment of Wireless Sensor Networks Dedicated to Fire Detection in Smart Car Parks using Chaos Whale Optimization Algorithm

Smart Car Parks (SCPs) based on Wireless Sensor Networks (WSNs) are one of the most interesting Internet of Things applications. This paper addresses the deployment optimization problem of two-tiered WSNs dedicated to fire monitoring in SCPs. Networks deployed inside the SCP consist of three types of nodes: Sensor Nodes (SNs) which cover the spots within the parking area, Relay Nodes (RNs) which forward alert messages generated by SNs, and the Sink node which is connected to the outside world (e.g, firefighters), through a high bandwidth connection. We propose an algorithm based on chaos theory and Whale Optimization Algorithm (WOA), which minimizes simultaneously the deployed number of SNs, RNs, and network diameter while ensuring coverage and connectivity. To evaluate the effectiveness of our proposal, we have conducted extensive tests. The results show that the Chaos WOA (CWOA) outperforms the original WOA in terms of solution quality and computation time and by comparison with an exact method, CWOA provides results very close to the optimal in terms of fitness value and is efficient in terms of computational time when the problem becomes more complex

A new scalable broadcast algorithm for multiport meshes with minimum communication steps

Many broadcast algorithms have been proposed for the mesh in the literature. However, most of these algorithms do not exhibit good scalability properties as the network size increases. As a consequence, most existing broadcast algorithms cannot support real-world parallel applications that require large-scale system sizes due to their high computational demands. Motivated by this observation, this paper makes two contributions. Firstly, in an effort to minimise the effects of network size on communication performance, this study proposes a new routing approach that enables the development of efficient broadcast algorithms that can maintain good performance levels for various mesh sizes. Secondly, based on the new routing approach, we propose a new adaptive broadcast algorithm for the mesh. The main feature of the proposed algorithm is its ability to handle broadcast operations with a fixed number of message-passing steps irrespective of the network size. Results from extensive comparative analysis reveal that our algorithm exhibits superior performance characteristics over those of the well-known Recursive Doubling and Extending Dominating Node algorithms

Logarithmic based backoff algorithm for MAC protocol in MANETs

Abstract: The Binary Exponential Backoff (BEB) is used by IEEE 802.11 Medium Access Control (MAC). BEB uses a uniform random distribution to choose the backoff value, that often leads to reducing the effect of window size increment. This technical report introduces a modified logarithmic backoff algorithm that uses logarithmic increment instead of exponential extension of window size to eliminate the degrading effect of random number distribution. Results from simulation experiments reveal that the new algorithm achieves higher throughput when in a mobile ad hoc environment

Tradeoffs between latency, complexity and load balancing with multicast algorithms

The increasing number of collective communication-based services with a mass interest and the parallel increasing demand for service quality are paving the way toward end-to-end QoS guarantees. Although many multicast algorithms in interconnection networks have been widely reported in the literature, most of them handle the multicast communication within limited performance metrics, i.e., either delay/latency or throughput. In contrast, this study investigates the multicast communication within a group of QoS constrains, namely latency, jitter, throughput, and additional traffic caused. In this paper, we present the Qualified Groups (QGs) as a novel path-based multicast algorithm for interconnection networks. To the best of our knowledge, the QG is the first multicast algorithm that considers the multicast latency at both the network and node levels across different traffic scenarios in interconnection networks. Our analysis shows that the proposed multicast algorithm exhibits superior performance characteristics over other well-known path-based multicast algorithms under different operating conditions. In addition, our results show that the QG can significantly improve the parallelism of the multicast communication